Method for production of ethyl alcohol

ABSTRACT

The invention describes a method for the economic production of ethyl alcohol involving dehydration of the alcohol in an adsorption-desorption process using ion exchange resins which have been swollen in water from about 50 to 300 times their weight.

The invention describes a method for producing ethyl alcohol byfermentation which introduces the following innovations:

a) Removal of contained water in a process of adsorption-desorption,

b) Energy self--sufficient production

c) Plant operation that does not cause any environmental pollution.

More specifically, our invention describes a method for the productionof ethyl alcohol by fermentation, in a highly original manner, with noenergy consumption and with low production cost. Raw materials to beused are sugars or sugars obtained by hydrolysis of cellulose andpentozanes which are widely found as they are the basic productsresulting from the function of metabolism. As such the invention offersan essential solution towards covering basic human necessities.

Today's world is facing a severe problem regarding the availability ofraw materials for the production of essential consumer products such aspolymers, synthetic products, detergents, and synthetic products foragricultural use. The fast consumption of crude oil reserves which arelikely to be depleted within the next 40 years creates potentialshortages in the production of such consumer products.

As a result, alternative sources of raw materials are already required,which are not subject to depletion like crude oil. Such a raw materialis ethyl alcohol which, if produced on a large scale and at a low costcan satisfy the needs in basic polymer materials, in detergents andsynthetic materials. However, the production of ethyl alcohol byfermentation methods from sugars results in 10% aqueous solutions and asa result, dewatering is necessary for its purification. This is effectedby successive distillations leading to alcohol strengths of 96%, whichconstitutes the final azeotropic mixture. To this mixture, benzene isadded and after successive distillations pure alcohol is produced.However, such methods are highly energy intensive consuming 20 to 60%more energy compared to what the product can give as a fuel.

Furthermore, during the production of ethyl alcohol by fermentation, alot of toxic and highly pollutant wastes are produced that can not behandled easily. This problem, along with those mentioned before, makethe production of ethyl alcohol by fermentation economically andproduction wise undesirable. As such fermentation alcohol until now hasbeen used only for the production of alcoholic beverages and issubjected to high taxation making it a very valuable material.Nevertheless, the production of ethyl alcohol by fermentation means hasbeen of great interest for the past 100 years. During the war, forexample, ethyl alcohol was produced on a large scale in Germany fromlignine cellulosic materials, by their hydrolysis in concentratedhydrochloric acid which was then distilled according to a method knownas the Bergius process. In the USA, after the war, the German method wasimproved by hydrolysing lignine cellulosic materials with sulphuricacid, in the presence of a catalyst and at high temperatures and specialconditions, according to a method known as the Scholler-Madison process,but once more this approach was not useful.

In the meantime, in Brazil, mass production of ethyl alcohol as a fuelhas been promoted, by making use of the molasses obtained from leachingof sugar canes. The wood like residues known as bagasse are used as fuelduring the production, and as a result the external energy requirementis reduced. However, the industrial wastes and the high volume ofrejected materials produced, cause severe environmental pollution andsince all these are discarded into the Amazon river it is clear that theenvironmental burden on it is getting very serious.

In the meantime, the EEC is promoting various improvements on thesemethods. One important achievement is the hydrolysis of cellulose withpure liquid hydrogen fluoride, which is a feasible solution since thehydrolysis is efficient and because the recycling of hydrogen fluorideby distillation has a low energy cost. The inventors, with financial aidfrom the EEC, have came up with a solution that uses the producedwastes, by digesting them anaerobically in the thermophilic region. Bythis method, substantial amounts of energy are produced and theenvironmental pollution problem is effectively tackled.

Following the above and the given the inventors' success in confrontingthe waste problem by producing useful energy from waste, intense effortswere made, aiming at the mass production of ethanol. The result is atechnologically original method by which the production of ethyl alcoholby fermentation is achieved at a low cost and without the creation ofenvironmental pollution.

The inventors have come up with an original and effective solution ofbiological separation ("biorefining") of lignine cellulosic materials,by which the components of these materials are separated by low costprocesses. The result is the separation of lignine cellulosic materialsinto pentozes, lignine and pure cellulose.

The separation of pentozes is effected through a hydrolysis process,that uses 0.5%-1.0% sulphuric or phosphoric acid as a catalyst, which attemperatures around 90°-130° C. produces pentozes fully hydrolysed intobasic sugars. 25-30% w/w of it is obtained and the soft material that isleft, which has a high content of cellulose is subjected, further on, toa deligninisation process. This is done by simple methods such as withoxygen enriched air, air and alkali or with chlorine, after whichlignine and the remaining quantity of pentozes are obtained. Lignine isseparated from the mixture easily by precipitating it with an alkali.

The obtained cellulosic mass is then subjected to hydrolysis withhydrogen fluoride in closed circuit where the hydrogen fluoride iscontinuously distilled and leaves a residue consisting of hydrolysedsugars, principally glucose.

The pentozes obtained from the process of pre-hydrolysis and from thepurification of the lignine, are mixed with the glucose that resultsfrom the cellulose hydrolysis, and are subjected to fermentation processfor the production of ethanol. They represent a quantity that is 70-75%of the original lignine cellulosic material, from which the productionof alcohol by means of modern and efficient processes results in alcoholyields around 60%. The invention partially refers to the biologicalseparation (biorefining) of lignocellulosics and in the effective usageof wastes resulting from alcoholic fermentation by anaerobic digestionin the thermophilic region, yielding increased quantities of energy inthe form of biogas that contains 85% methane. The alcoholic fermentationand the cellulose hydrolysis by hydrogen fluoride were already known.

In addition to the sugars already mentioned other sugars are used thatcontain mainly glucose and pentozes such as carrob sirup, molasses,sugarcane hydrolysis residues, sugars from raisins and figs etc. whichto date are successfully used for the production of ethanol.

Furthermore, the invention refers in an original and determined mannerto the process of alcohol purification from the aqueous solution by theprocess of adsorption-desorption which is a low cost separation and doesnot consume energy until pure ethanol is obtained.

We have created products, which are ion-exchange resins proven to bevery efficient in separating alcohol from the aqueous solutions,yielding pure ethanol. These products exhibit maximum ion-exchangepotential of 5.8-6.0 and are advantageously swollen in water up 300times their weight. They contain sulfonic groups in high density and assodium salts they exhibit a large tendency to adsorb water and arelatively low tendency to adsorb ethanol, resulting in complete andeffective dewatering of ethanol.

These materials of selective adsorption are polymeric materials, whichafter special restructuring have acquired a macromolecular chemicalstructure, characterised by high chemical stability and allows for theintroduction of sulfonic groups at high densities in the macromolecularstructure with Mc 50. 000. The next stage is to achieve the desorptionof water followed by recycling of the adsorbing media. This is simplyand originally achieved by creating osmotic conditions which is effectedby immersing the materials in the adsorbed stage into a sodium chloridesolution of a strength of 3-30%, or by immersing them in sea water,which creates osmotic pressure resulting in the water flowing out fastfrom the polymeric material which is shrunk in a form that allows fortheir recycling.

Following the adsorption and consequent desorption of water thefollowing results are achieved as shown in table 1.

                  TABLE 1                                                         ______________________________________                                        Alcohol losses during the process of adsorption-desorption.                   Adsorption area                                                                             30-60%     60-90%    90-100%                                    Ion exchange        Alcohol losses % potential,                               ______________________________________                                        Swell 200                                                                     5.3           1%         1%        1.2%                                       5.5           0.6        0.7       0.8                                        5.7           0.4        0.5       0.6                                        5.9           0.1        0.1       0.1                                        6.0           0.08       0.07      0.07                                       Swell 100                                                                     5.7           0.3        3.35      0.4                                        5.9           0.1        0.1       0.09                                       6.0           0.008      0.01      0.01                                       ______________________________________                                    

According to the results of table 1 the materials used promote theprocesses of adsorption and desorption to highly effective andadvantageous standards. The production of pure ethanol is achieved andthe desorption shows that the alcohol losses, can be negligible withinerror limits, when perfect conditions prevail regarding ion-exchangerate and swelling degree of the polymer materials. In other words, theinvention offers a solution for producing ethyl alcohol fromagricultural products and by-products, following their biologicalseparation to their constituent materials and maximisation of theorganic mass to be fermented to alcohol. Then the alcohol is separatedfrom the water in an original and effective way. This is done bysubjecting the alcohol-water mixture to a adsorption-desorption process,combined with effective usage of the resulting wastes to produce energyin a pollution free manner, so that ethanol is produced on a large scaleand at high standards.

The process that the method proposes for the production of ethyl alcoholon a large scale end economically is as follows:

The lignine cellulosic materials, after being processed for biologicalseparation and hydrolysis of cellulose, yield 70-75% fermentable sugars,with lignine isolated representing 15% w/w. Waste materials are producedfrom unused organic materials in the order of 6-10% and fermentationwastes containing about 30% of organic material based on the total mass.From these waste and organic residue materials, following theiranaerobic digestion in the thermophilic region, 20% w/w biogas isproduced containing 85% methane and a calorific value of 8,000 kcal/kgwhich is equivalent to 160,000 kcal/100 kg of cellulosic material. Thisrepresents an amount of energy capable of supporting the entireproduction process of hydrolysing the cellulose, which requires about20,000 kcal, and for the first distillation of the fermentation brothwhich separates the waste material yielding an alcohol distillate of 35%in alcohol, which is estimated to require thermal energy in the order of120,000 kcal.

This alcohol solution is then subjected to the adsorption-desorptionprocess in the system of ion-exchange resins mentioned, at a swellingdegree of 200, ion-exchange coefficient of 5.9, which finally yields 99%pure alcohol of excellent quality and purity. The alcohol losses duringthe process is in the order of 0.1%. The ion-exchange resins followingthe alcohol-water separation are immersed in a 15% sodium chloridesolution or simply in sea water, and by virtue of the osmotic pressurethat is produced the adsorbed water is rejected and the resins areobtained in shrunken form ready to be reused.

Alcohol production from plain sugars according to the method is effectedin exactly the same way. However, the energy produced from the wastematerial resulting from its anaerobic digestion, will be capable ofcovering only the first distillation separating the 35% alcohol andwater.

The invention according to its previous description, refers to acomplete solution for producing ethanol on a large scale from ligninecellulosic materials or sugars at low cost with complete energyself-sufficiency and without causing environmental pollution. Theethanol that will be produced according to the method can be used as afuel or as raw material for the production of polymers (e.gpolyethylene), detergents, and synthetic raw materials for a multitudeof uses and for agricultural applications.

EXAMPLE 1

a. Wheat straws are brought into a tank where the temperature ismaintained at 95° C. by the addition of steam. The tank has a capacityof 2 cubic meters and is filled with 1.5 cubic meter of water with acatalyst and 150 kg. of straw. The following catalysts have been usedwith the respective concentration in water:

    ______________________________________                                                   Catalyst  Concentration                                            ______________________________________                                        I            H.sub.2 SO.sub.4                                                                          2-3%                                                 II           Hcl         2-3%                                                 III          PO.sub.4 H.sub.3                                                                          4-6%                                                 ______________________________________                                    

Following heating for three hours, the straws are removed and compressedat 10 atmospheres. The collected liquids have the following sugarcontent:

I 23.9% II 23.1% III 23%

The remainder solid cellulosic material in a dry condition is:

I 66.1% II 67.1% III 65.2%

b. The same process has been applied to pieces of poplar-tree wood ofdimensions ranging from 3 to 5 cm. The following results were obtained:

Sugar composition

I 21.2% II 23.4% III 22.8%

Solid Remainder

I 69.3% II 70.5% III 71%

c. The same process has been applied to cotton stems. The followingresults were obtained:

Sugar composition

I 24.1% II 24.8% III 25.3%

Solid Remainder

I 66.4% II 63.8% III 61.9%

d. The same process has been applied to rice straw. The followingresults were obtained:

Sugar composition

I 20.8% II 21.4% III 22.6%

Solid Remainder

I 66.8% II 67.1% III 66.4%

The sugar produced during the processes a-d above are common sugar to anextent of 90-92%. Following further heating of their solution at100°-120° C. for 1-2 hours, they are totally converted to simple sugarof the following composition:

    ______________________________________                                               Xylose         70-75%                                                         Arabinose      10-15%                                                         Mannose        5-6%                                                           Lactose        3-8%                                                           Glucose        5-8%                                                    ______________________________________                                    

The above processes have been carried out at temperatures in excess of95° C. or at temperatures of 120°-150° C., where lower concentrations ofacid catalysts and processing times are required. Furthermore, resultsobtained are perfect in terms of sugar hydrolysis and quality.

EXAMPLE 2

The cellulosic remainders from example 1 are subjected to adelignisation process in the presence of a) chlorine, b) oxygen, c)atmospheric air.

a. Delignisation in the presence of chlorine

Yield of cellulosic material: 43-44% (fracture length 6500 m.,perforation index: 6, number of bends: 500)

Yield in Sugar: 8-10%

Chlorine Absorption: 15-25% w/w

b. Delignisation in the presence of oxygen

Yield of cellulosic material: 43.8% (fracture length 4800 m.,perforation index: 5, number of bends: 450)

Yield in Lignine: 12%

Yield in Sugar: 16%

Conditions of processing: NaOH 16%, MgCO₃ 1% at 120° C., Oxygen at 5atm., Flow: 1.8 litters/hour

c. Delignisation in the presence of air

Yield of cellulosic material: 43.4% (fracture length 4750 m.,perforation index: 5, number of bends: 440)

Yield in Lignine: 14%

Yield in Sugar: 15%

Conditions of processing: NaOH 16%, MgCO₃ 1%, anthraquinone 1%, airpressure=10 atm., Flow: 2.8 litters/hour

EXAMPLE 3

The cellulosic material of example 2 are subjected to hydrolysis withhydrogen fluoride in specially arranged reactors which are defined bythe space for the mixing of the cellulosic material with hydrogenfluoride and by the space for the separation of hydrogen fluoride bydistillation for recycling.

Five volumes of hydrogen fluoride are added per volume of cellulosicmaterial

One volume of water is also added

The mixing of the cellulosic material with hydrogen fluoride leads tothe complete hydrolysis of cellulose. Hydrogen fluoride is recycled bydistillation and glucose is collected in an aqueous solution of aglucose concentration of 30-35%.

EXAMPLE 4

Sugars produced as per examples 1, 2 and 3 are subjected to fermentationfor alcohol production, according to usual procedures:batch--semi--batch process or continuous process.

Sugars produced as per the examples 1, 2, 3 above are mixed and have amean composition of:

Pentoze 40-50%, Hectoze 50-60%, mainly Glucose

Alcohol production from sugar of the above composition using modernoptimised production processes is in the order of 59-60% w/w.

Total sugar from the various processes of biological separation oflignine cellulosic materials, have the following composition:

a: Glucose 55%, Xylose 31%, Arabinoze 8%, Mannoze 3%, Lactoze 3%

b: Glucose 65%, Xylose 16%, Arabinoze 9%, Mannoze 4%, Lactoze 8%

c: Glucose 52%, Xylose 33%, Arabinoze 7%, Mannoze 3.5%, Lactoze 4.5%

EXAMPLE 5

The product of fermentation for alcohol production is subjected todistillation for the separation of effluent water and alcohol which isreceived in the distillate at a concentration of 35%. The effluent waterhas a high environmental load: BOD 30,000-40,000, COD 60,000-120,000 andsuspended organic solids 10-12.%. The effluent water at 80° C. issubjected to anaerobic digestion in the thermophilic region for theproduction of energy in the form of 0.5 cubic meters of biogascontaining methane at a ratio of 85% per kg. COD. The energy generatedfrom the effluents and 5-10% of other organic waste is enough for allenergy required for the hydrolysis of cellulose as described in example3 and for the energy requirements for the distillation of thefermentation product described in this example.

EXAMPLE 6

A 35% alcohol solution is fed to a system of ion exchanging resins whichare arranged along a longitudinal column in a manner so that theswelling coefficient of resins at the top of the column is 250, whereasthat for resins at the bottom of the column is 50. The resins areselected so as to exhibit a maximum ion exchanging coefficient of 5.9 to6.5. The length of the column depends on the required result: Theproduct at the end of the column must be pure alcohol, free of anywater. When saturated, the column is regenerated simply and quickly byimmersion in a solution of sodium chloride of a strength between 3 and30%, or by immersion in sea water, where due to the osmosis effect, allthe adsorbed water flows out and the resins recycled.

Alcohol losses due to adsorption by the resins along with water arenegligible, usually in the order of 0.1 to 1%.

We claim:
 1. A method for the production of ethanol by fermentation,comprising the steps of:fermenting a sugar composition to produce afermentable product containing ethanol; subjecting said fermentableproduct to distillation to produce an ethanol solution and wasteproduct; removing water from the ethanol solution through anadsorption-desorption sequence, wherein ion exchanging resins having anion exchanging coefficient value of 5.3-6.5 are used to separate ethanolfrom water, wherein said resins are swollen in water to about 50 to 300times their weight and adsorb essentially all of the water of theethanol-water mixture until essentially pure alcohol is produced; andanaerobically digesting said waste product to produce energy sufficientto conduct said method.
 2. The method according to claim 1, wherein saidsugar composition is obtained from lignine cellulosic materials.
 3. Amethod for the production of ethanol by fermentation, comprising thesteps of:fermenting a sugar composition to produce a fermentable productcontaining ethanol; subjecting said fermentable product to distillationto produce an ethanol solution and waste product; removing water fromthe ethanol solution through an adsorption-desorption sequence, whereinion exchanging resins are arranged in a column, where the swell ratio ofthe resins arranged along the column is gradually reduced from top tobottom, wherein resins at the top of the column have a swell ratio of250-300 and those at the bottom of the column have a swell ratio of40-50, wherein water retention is gradually conducted along the columnand essentially pure ethanol is collected at the bottom; andanaerobically digesting said waste product to produce energy sufficientto conduct said method.
 4. The method according to claim 3, wherein saidsugar composition is obtained from lignine cellulosic materials.
 5. Themethod according to claim 1, wherein said ion-exchange resins havemaximum ion exchanging coefficient value of 5.8-6.0, and containsulfonic groups in high density as sodium salts.